Echo sounders



Sept. 27, 1955 ROLFE 2,719,280

ECHO SOUNDERS Filed March 15 195] United States Patent 2,719,280 ECHOsoUNnERs Denis Hugh Rolfe, Gidea Park, England, assiguor to MarconiSounding Device Company Limited, London, England, a company ofGreatBritain Application March 13, 1951, Serial 'No. 215,200 Claimspriority, application Great Britain March 27, .1950

1 Claim. (Cl. 340-3) This invention relates to echo sounders and has forits object-t0 provide improved means -for producing from a comparativelylow voltage source a high voltage pulse for operating an echo soundingtransmitter.

It is common-echo sounding practice to obtain a pulse for transmissionby discharging a condenser through the winding of a magneto-strictiveprojector. For any given projector there -is usually an optimum value ofcondenser capacity and, of course, output 'power depends on the initialcharge on the condenser. 'For sounding in great depths or for suchpurposes as detecting shoals of fish, a very high peak power is requiredand, for such purposes, it is common to use a condenser charged to 1000volts or more. The obtaining of a direct :current voltage as high asthis involves, with I known arrangements, the use of a costly and largerectifier or low utilization factor.

Where the transmitting projector is also used for reception it is ofadvantage to restrict the condenser discharge to the first half cycle inorder to maintain the residual magnetism of the magneto-strictiveprojector and leave it suitably polarized for reception. One known wayof doing this is to control the discharge of the condenser by a coldcathode gas filled tube arranged to be non-conducting until a suitabletrigger pulse is applied to it and applying such a pulse when it isdesired to transmit. With such an arrangement the main dischargecontinues until the current falls to zero, whereupon the tube ceases toconduct. The result is therefore, that only the first half cycle ofdischarge takes place as is desired. However, with known arrangements ofthis nature tubes capable of passing peak currents of the order of from50 to 150 amperes are necessary. So long as the operating voltage isfairly low e. g. up to about 400 volts, neon filled tubes can besatisfactorily used for currents of this order. For higher voltages,

speaking, the only types at present available which are suitable forsuch high currents but a mercury vapor filled tube for operating at 1500volts and capable of passing a peak current of 150 amperes has theserious practical defects of being large, heavy, costly and requiringcareful handling.

The present invention seeks to overcome these difiiculties and defectsand to provide improved and relatively simple arrangements employingrelatively inexpensive discharge devices and capable of producing a highvoltage, high peak current discharge from a relatively low voltagesource, preferably the source already normally provided as the anodevoltage source for the echo sounder receiver circuit.

According to this invention an echo sounder wherein a high voltage highpeak current discharge is required for transmission comprises aplurality of condensers, means for charging said condensers in parallelfrom a voltage source, and a plurality of discharge devices the first ofwhich is a triggered device and each of which 7 however, tubes filledwith mercury vapor are, practically (except the last) is soconnectedthat, when it becomes conductive, it adds the charge voltage or voltageson the condenser :or-condensers'on the voltage supply source sidethereof to the voltage charge on the condenser next on -the other sidethereof, means being provided for triggering the first device and eachofthe other devices being such'as to be unable to withstand the sumofthe charge voltage of the condensers on the voltage source side thereof,the final discharge device being connected in series with the echosounding :transmitter.

'In :the preferred and simplest embodiments of the invention there are.only'two condensers and two discharge devices, which are so connectedthat, when the discharge devices are non-conducting, the condensers arecharged in parallel through resistance inseries, but upon theapplication of a triggering voltage to one of the discharge devices tobreak it down, the voltage in the first condenser is added in series tothat in the second to produce a sum voltage which is suflicient tobreakdown the second discharge device and discharge both condensers in'a :series circuit through the transmitter.

The invention is illustrated inthe accompanying drawings in which Figs..1 :and 2 show diagrammatically two embodiments thereof.

Referring to Fig. 1 a voltage source (not shown) preferably the normallyprovided anode voltage supply source for the echo sounding receiver=hasits negative terminal :1 grounded and its positive terminal 2 connectedthrough a series circuit including a first resistance 3, theanode-to-cathode space of a1first-cold cathode gas :filledrelay tube-4and .the coil 'of thefecho sounding transmitter (represented only bysaid coil) back to ground. The relay tube 4 has its anode 6 towards thepositive terminal 2 and is of a known type having, in addition to theanode, a cathode 7 and two grids 8 and 9. The grid 8 nearer the cathodeis connected thereto through a resistance 10. A potentiometer consistingof two further resistances 11, 12 in series is connected across thesource, a condenser 13 being shunted across that of resistance 12 whichis on the negative side. The remaining grid 9 of the relay tube 4 isconnected to the junction point of the two resistances 11, 12 through aresistance 14. The anode 6 of the said relay tube 4 is connected throughtwo parallel branch circuits to ground, the first branch circuitconsisting of a first main condenser 15 in series with a resistance 16and the other consisting of a resistance 17 in series with a second maincondenser 18, these elements being in the order stated, in each case.The anode 19 of a second similar gas filled relay tube 20 is connectedto the junction point of the elements 17, 18 and the cathode 21 thereofis connected to the junction point of the elements 15, 16. The grid 22of the second relay tube which is nearer the anode thereof is connectedthrough a resistance 23 to the junction point of the resistances 11, 12and the remaining grid 24 is connected to ground through a resistance25. The said grid 24 is also connected to ground through a condenser 26and a transmitting key 27 (or through a pair of transmitting contacts),the junction point of said condenser 26 with said key or contacts beingconnected to the junction point of the resistances 11, 12 through yetanother resistance 28.

With this arrangement, so long as the gas filled relay tubes are notconductive, the two main condensers 15, 18 are charged in parallel tothe voltage of the supply source. On closing the transmitting key orcontacts, however, a triggering pulse is applied to the control grid 24of the relay tube 20. This pulse causes the relay tube to ionize so thatthe voltage across it falls almost to zero. The voltage across the relaytubes 4 accordingly rises towards a value equal to twice the supplyvoltage value.

The said relay tube 4 is, however, unable to withstand this voltage-inpractice, the relay tube may conveniently be chosen to break down whenthe voltage across it exceeds that of the supply source by about 30voltsand accordingly itbreaks down and a voltage approaching twicethesupply'voltage appears across the transmitter coil .T, and the maincondensers 15, .18 discharge therethrough in series. When the dischargecurrent falls to zero the gas filled relay tubes extinguish and the maincondensers recharge.

The arrangement shown in Fig. 1 may be regarded as a two stageembodiment but, as already stated, the invention may. be carried intopractice with as many stages .assare desired or are necessary to obtainthe required highdischarge voltage from the relatively low voltagesupply source. .Thus, as shown in Fig. 2, there may be four maincondensers here designated C1, C2, C3, C4 andfour .gas filledrelaytubeshere designated R1, R2, R3,.R4, the condenserscharging in parallel solong as the .gas filled relay tubes are non-conductive. The relay.tubesand condensers are connected as shown so that when the first relay tubeR1 is triggered, the chargein .thefirst condenser C1 is added to thevoltage across the second relay tubeRZ causing it to break down and addthe sum of the voltages in the first two condensers C1, C2 to thatacross the third relay tube R3, which in turn breaks down and adds thesum of the voltages in the first three condensers C1, C2, C3 to thatacross the fourth relay tube R4 which in turn breaks down and dischargesthe sum voltage clue to all four condensers C1, C2, C3, C4 in seriesthrough the transmitter coil T.

What I claim is:

An echo sounder transmitter arrangement comprising a voltage source, anecho sounding transmitter, a plurality of condensers, circuits includingsaid condensers for charging said condensers in parallel from saidsource, a plurality of discharge devices each constituted by a coldcathode gas filled relay having a cathode, an anode and at least onetriggering grid between said anode and cathode, means for applying atriggering potential to the triggering electrode of the first of saiddevices, circuits connecting each of said devices except the lastbetween two of said condensers to add, when conductive, the chargevoltage or voltages on the condenser or condensers on the voltage supplysource side thereof, each of said devices except the first having abreakdown voltage below the sum of the charge voltage of the condenserson the voltage source side thereof, the final discharge device beingconnected in series with the echo sounding transmitter, wherein an inputcircuit is arranged between said voltage source and said first mentioneddischarge device, said input circuit including a pair of resistancesconnected in series and connected across said voltage source and aconnection including a further condenser and a further resistance inseries between the junction point of said pair of resistances and thetriggering grid of said first mentioned discharge device, anotherresistance connected between said triggering and earth and a switchconnected across the further condenser and the last mentioned resistancein series.

References Cited in the file of this patent UNITED STATES PATENTS

